The present invention relates to a water-soluble dietary fiber-containing composition useful in the production of functional foods and a method for the preparation of the same.
Raw materials for foods having functional characteristics have attracted the attention of many people in proportion to the recent increased population of the health-oriented persons. There have recently been put on the market a large number of and a wide variety of foods, which make the most use of the raw materials possessing functionality, in consideration of the present conditions of the consumers concerning foods. There can be mentioned, for instance, dietary fibers as one of such raw materials for foods. The dietary fibers possess a variety of beneficial physiological functions and they are relatively cheap raw materials for foods. For this reason, they have become of major interest lately as raw materials for functional foods and have widely been used.
Raw materials for dietary fibers include water-insoluble ones and water-soluble ones. Examples of such water-insoluble raw materials for dietary fibers are cellulose, wheat bran, fibers originated from apples, fibers derived from sweet potatoes, and chitin. The water-soluble raw materials for dietary fibers are roughly divided into high viscous ones and low viscous ones and examples of such high viscous water-soluble raw materials are pectin, powdered konjak (mannan) (powdered devil's tongue), alginic acid salts, propylene glycol ester of alginic acid, guar gum, and agar; while examples of lowly viscous water-soluble raw materials are hardly digestible dextrin, polydextrose, branched maltodextrin, inulin and guar gum hydrolysates. These substances possess various kinds of physiological functions such as the reduction of the content of cholesterol, the inhibition of an increase in the blood sugar level, the regulation of intestinal function, the prevention of carcinoma of large intestine and the excretion of harmful substances.
In addition, there can likewise be listed, for instance, oligosaccharides as a kind of raw materials for dietary fibers. The oligosaccharide is a lowly viscous and water-soluble saccharide and it has a wide variety of functionalities such as a hypocariogenic effect, low-caloric characteristics, regulation of intestinal function and a Bifidus bacteria-proliferation function. Typical examples of such oligosaccharides are fructo-oligosaccharides, galacto-oligosaccharides, and xylo-oligosaccharides.
Incidentally, as has been described above, there have recently been put on the market a wide variety of foods to which various functionalities are imparted while making the most use of the raw materials for dietary fibers. However, each food should be inherent in beautiful feeling or appearance, even if it has a specific function such as a physiological one and it should satisfy various requirements or possess the essential elements inherent in or peculiar to the food per se such as the beautiful appearance, taste and palatability as well as fine flavor.
Among the raw materials for dietary fibers, raw materials fundamentally easily used in foods include water-soluble ones each having a low viscosity value (such as hardly digestible dextrin, polydextrose and branched maltodextrin) and oligosaccharides and these raw materials can be incorporated into water-soluble foods such as beverages, soup and yoghurt in any required amount without any difficulty. In foods in the form of solids such as bakery's foods, however, some problems arise such that the working properties of raw materials for such foods are impaired and that the resulting foods have deteriorated quality such as taste and palatability, as the added amount of such dietary fibers increases. For instance, when hardly digestible dextrin is incorporated into breads, the dietary fibers can be used in an amount of not more than 8% by mass on the basis of the total mass of the flour used without adversely affecting the working properties of the raw materials for such foods and the quality of the resulting foods. On the other hand, if hardly digestible dextrin is incorporated into a Food for Specified Health Use in an amount of not less than 12% by mass on the basis of the total mass of the flour used, for ensuring an effect of inhibiting an increase in the blood sugar level or a regulation of intestinal function, it has been confirmed that the formation of gluten is inhibited due to the highly water-soluble characteristics of the hardly digestible dextrin and that this in turn leads to a variety of drawbacks such as the obstruction of the molding of the resulting dough, the reduction of the working properties, and the deterioration of the quality of the resulting food, for instance, the formation of a food having extremely soft taste and palatability.
Moreover, in case of water-soluble and highly viscous dietary fibers (for instance, thickening polysaccharides such as alginic acid and agar) among others, problems arise, if they are used in breads and the added amount thereof increases, such that the quality of the resulting food is deteriorated, for instance, the food has a rather hard feeling when eating the same. For this reason, these dietary fibers have been incorporated into these foods only in a small amount for the purpose of improving the quality of the resulting foods and/or the working properties of raw materials therefor.
Up to now, there have been proposed various improving means which permit the addition of a large amount of dietary fibers, in particular, water-soluble dietary fibers to bakery's foods or noodles or vermicelli, to solve these problems.
Patent Document 1 proposes a method for the addition of hardly digestible dextrin as water-soluble dietary fibers in the principal kneading step of the sponge dough method during the kneading process when producing a bakery's product, but these means are not sufficient for improving the bread-preparation aptitude (working characteristics in bread-production), and for improving the taste, palatability, internal phase and appearance of the resulting breads.
Patent Document 2 proposes a baking food comprising wheat dough and dietary fibers coated with oils and fats and dispersed in the dough as well as a method for the preparation thereof, but this method is likewise insufficient for the improvement of the kneading characteristics (working characteristics in food-production), and the taste and palatability of the resulting food.
Patent Document 3 proposes a method for preparing noodles, bakery's foods and snack food, which comprise a composition containing a water-soluble dietary fiber material and modified starch and incorporated into these foods. However, this method is not sufficient for improving the kneading characteristics (working characteristics in food-production), and the taste and palatability of the resulting food.
Patent Document 4 proposes a method for the preparation of dietary fiber-fortified noodles, which makes use of fine cellulose-containing composite material as a principal ingredient when preparing noodles, but this method does not permit the solution of the problem concerning the taste and palatability of the resulting foods and it also suffers from a problem such that it requires increased production cost.
Patent Document 5 proposes a method for the preparation of dietary fiber-enriched breads, which makes use of fine cellulose-containing composite material as a principal ingredient, but this method does not permit the solution of the problem concerning the taste and palatability of the resulting foods and it also suffers from a problem in that it requires increased production cost.                Patent Document 1: JP-A-4-51840;        Patent Document 2: JP-A-8-289715;        Patent Document 3: JP-A-10-243777;        Patent Document 4: JP-A-2000-316507; and        Patent Document 5: JP-A-2001-45960        